JPH0542033Y2 - - Google Patents

Description

[Detailed explanation of the idea]

INDUSTRIAL APPLICATION FIELD The present invention relates to a packaging bag that uses a cross-linked stretched polyethylene film as a sealant and has excellent cutability, moisture-proof optical properties, and oil resistance. Conventional technology Packaging bags have various characteristics such as heat sealing strength required to package and seal the packaged items, optical properties required for display effects, moisture and oil resistance to protect the contents, and cutability when opening. functionality is required. Conventionally, films such as polypropylene (PP), linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), ethylene-vinyl acetate copolymer (EVA), and ionomer have been used as sealant layers for packaging bags. There is. However, although polypropylene unstretched film (CPP film) has oil resistance, its cutting properties are insufficient, so a layer of polyethylene uniaxially stretched film is used, but it tends to generate hairs when cut. Clear cutting properties are insufficient. On the other hand, low-crystalline polyethylenes such as LDPE and EVA have insufficient cutting properties and oil resistance.
Moreover, these laminated films do not necessarily have sufficient optical properties. In addition, when providing moisture resistance, polypropylene biaxially stretched film (OPP film) is used.
It was necessary to further combine these. Problems to be solved by the invention This invention was made to solve the above-mentioned problems.
The purpose of the present invention is to provide a packaging bag with excellent optical properties, moisture resistance, and oil resistance. Means for Solving the Problems The present invention achieves the object by using a stretched polyethylene film having a specific degree of crosslinking in the thickness direction of the film for installing a sealant on a packaging bag. That is, in the present invention, the inner layer 1 is made of high-density polyethylene, and is a biaxially stretched polyethylene film in which the degree of crosslinking decreases inward in the thickness direction of the film, and the outer layer 2 has a heat shrinkage rate of 5% at 140°C.
1. A packaging bag made of a composite film which is at least one of the following laminated materials, characterized in that biaxially stretched polyethylene films facing each other in the inner layer 1 are overlapped and heat-sealed. Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings. FIG. 1 is a perspective view of the four-sided sealed bag of the packaging bag of the present invention in an open state, and FIG. 2 is a partially enlarged sectional view of the same. In the figure, 1 is the inner layer of BOPE film, and 2 is the outer layer of laminated material. This outer layer 2 is
Paper, aluminum (Al) foil, cellophane, heat-resistant plastic film, etc. This laminate may be a single material or a composite material. The structure of the inner layer 1 and outer layer 2 is, for example, BOPE film/paper,
BOPE film/Al foil, BOPE film/heat-resistant plastic film BOPE film/Al foil/
Heat-resistant plastic film, BOPE film/
Examples include heat-resistant film/heat-resistant film. These composite films are formed by adhering an outer layer 2 to one side of a BOPE film by dry laminating with a urethane adhesive or wet laminating with an EVA emulsion adhesive or the like. Also, 3 is inner layer 1
Layer the BOPE film sides together and heat seal the periphery to form a bag.
This is the part that was pasted. The BOPE film of the inner layer 1 is made of high-density polyethylene, and the degree of crosslinking decreases toward the inside in the thickness direction of the film. Particularly preferably, it is made of polyethylene with a density of 0.95 g/cm ³ or more and an MI of 0.5 to 20 g/10 minutes, and the degree of crosslinking constitutes a crosslinked layer/uncrosslinked layer/crosslinked layer in the thickness direction of the film, and the gel content is The ratio (proportion of insoluble portion by boiling p-xylene extraction) is 20 to 70% by weight for the crosslinked layer, and 20 to 70% by weight for the uncrosslinked layer.
It is a biaxially stretched film in which the composition ratio of each layer is 0% by weight, uncrosslinked layer: crosslinked layer on both sides 1:0.1 to 10, and the stretching ratio is 3 times or more in one direction and the area magnification is 9 times or more.
This film is transparent, has excellent moisture resistance, and has good cutting properties. The thickness of this film is appropriately selected depending on the intended use, but is usually about 10 to 50 μm. The manufacturing method of such a BOPE film is described in Japanese Patent Application Laid-open Nos. 59-174322 and 61-
This is disclosed in Publication No. 74819, etc. The BOPE film may be coated with Al vapor deposition, polyvinylidene chloride coating, or the like. In addition, the laminated material of the outer layer 2 described above is used in order to impart heat-sealing properties that do not impair cosmetic properties to the BOPE film of the inner layer 1, which cannot be heat-sealed with a single layer.
It is necessary that the heat shrinkage rate at 140°C is less than 5%. Examples of laminated materials include paper such as high-quality paper and bleached kraft paper, Al foil, cellophane, heat-resistant plastic film, and materials such as polyester, ethylene-polyvinyl alcohol copolymer, polyamide, polyparabanic acid, polyimide, etc. can give. The type, combination, thickness, etc. of these outer layers may be appropriately selected depending on the purpose and use. The packaging bag of the present invention is not limited to a four-sided sealed bag, but may also be a three-sided sealed bag or a pillow packaging bag. Example Next, an example of the present invention will be shown, but the present invention is not necessarily limited to this example. The evaluation method for the examples is as follows. (1) Haze: JISK 6714 (2) Moisture permeability: JISZ 0208 B method (3) Heat sealing strength: JISZ0238 (4) Cutting property: Put an I-shaped notch in the seal part of the bag and cut it by hand to make it almost straight. Items that can be cut precisely are marked as ○, and items that can be cut in an inconsistent direction are marked as ×. (5) Oil resistance: Place unbleached kraft paper under the composite film used for the bag, place 5g of margarine on the composite film, leave it at 60℃ for 24 hours, and evaluate from the degree of seepage into the unbleached kraft. did.
Note that in the case of a composite film with paper, kraft paper is omitted. No oozing was rated as ○, partial oozing was rated as △, and obvious oozing was rated as ×. (6) Heat shrinkage rate: A test piece (width 10
mm x length 350 mm) (taken vertically and horizontally) for 10 minutes, and the heat shrinkage was determined from the length L ₀ before heating and the length L ₁ after heating of the test piece. The rate was calculated. Heat shrinkage rate = (L ₀ −L ₁ /L ₀ )×100 Example 1 High-density polyethylene (density 0.957 g/cm ² , MI
1.0g/10 minutes) and crosslinked by electron beam irradiation [gel fraction (wt%) = crosslinked layer/
Uncrosslinked layer/crosslinked layer = 50/0/50 crosslinked composition ratio = crosslinked layer: uncrosslinked layer: crosslinked layer = 1:1.75:1] at 127°C.
High-density polyethylene biaxially stretched film (BOHD film) with a thickness of 20μ after being stretched vertically x horizontally = 4 x 6 times.
I got it. This film has a haze of 2.7% and moisture permeability.
It was 3.6g/m ² /24hrs. Next, this BOHD film was coated with EVA emulsion adhesive (3 g/m ² ), and high-quality paper (20 g/m ² ) was wet laminated to form BOHD/
I got a paper film. This composite film
The overlapping periphery was heat-sealed with a heat-seal bar at 180°C so that the BOND film surfaces faced each other to obtain a packaging bag. The characteristics of this bag are shown in Table-1. For comparison, instead of BOHD film,
LDPE extrusion laminated paper with a thickness of 20μ/
LDPE composite film, and PP90% and LDPE10%
Example 1 Regarding a composite film of paper/ELPP made by extrusion laminating a composition (ELPP) of 20 μm in thickness.
A packaging bag was obtained in the same manner as above. The characteristics of the bag are also listed in Table-1. Example 2 After applying a urethane adhesive to a polyethylene terephthalate (PETP) film (12μ), the BOHD film of Example 1 was dry laminated,
A composite film was obtained. The haze of this composite film was 3.5%. This composite film was heat-sealed in the same manner as in Example 1 to obtain a packaging bag. The characteristics of this bag are also listed in Table-1. For comparison, instead of BOHD film,
Dry laminated with LDPE film (30μ)
A PETP/BOHD composite film was obtained. The haze of this film was 8%. A packaging bag was obtained from this composite film in the same manner as in Example 2. The characteristics of the bag are also listed in Table-1. Example 3 BOHD of Example 1 was attached to the PETP film (12μ) via Al foil (9μ) using urethane adhesive.
Dry laminate the film, PETP/Al/
A composite film of BOHD was obtained. This composite film was heat-sealed in the same manner as in Example 1 to obtain a packaging bag. The characteristics of this bag are also listed in Table-1. Example 4 In Example 2, Al was used instead of BOHD film.
Using vapor-deposited BOHD film, the Al-deposited surface is PETP
A composite film of PETP/Al-deposited BOHD laminated on the sides was obtained. A packaging bag was obtained by heat sealing in the same manner as in Example 1. The characteristics of this bag are also listed in Table-1.

[Table] Effects of the invention In the packaging bag of this invention, BOPE film, which is difficult to heat seal in a single layer, is made into a composite film made of a specific laminated material, and the BOPE film surface is used as an inner layer and a heat sealant layer. It has superior moisture and oil resistance compared to conventional products, and also has excellent straight and clear cutting properties.
In addition, when the package is made of a composite film with a transparent laminated material, the package does not impair its optical properties.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an open state of a four-sided sealed bag of the packaging bag of the present invention, and FIG. 2 is a partially enlarged sectional view of the same. 1...Inner layer, 2...Outer layer, 3...BOPE film heat-sealed part.

Claims (1)

[Scope of utility model registration request] The inner layer 1 is made of high-density polyethylene, and is a biaxially stretched polyethylene film in which the degree of crosslinking decreases inward in the thickness direction of the film, and the outer layer 2 is
1. A packaging bag comprising a composite film which is at least one type of laminated material having a heat shrinkage rate of less than 5% at 140° C., characterized in that biaxially stretched polyethylene films facing each other in the inner layer 1 are overlapped and heat-sealed.